Noise generated in a clean-room environment, a room for use as for example in food processing, needs to be attenuated in order to allow for minimizing the background noise to at least within the limits specified by the Occupational Safety and Health Administration (OSHA). Numerous devices have been developed to effectively absorb sound, acoustical tile and other perforated sound absorbing material are examples. The problem of absorbing sound in a clean-room environment requires that the sound absorbing panel preferably have few areas in which organic growth can be supported and must be easily cleanable. While solutions to this problem have been found, U.S. Pat. No. 4,301,890 to Zalas is illustrative, such honeycomb diaphragm type panels are inherently expensive and still have the problem of puncture, since the membrane is simply stretched over the honeycomb area as a drumhead would be stretched over a drum body.
Heretofore, many different other methods have been utilized in an effort to make porous material suitable as sound absorber for clean-room, sanitary enrironments. These methods include inter alia the covering of traditional porous type acoustical ceiling tile with washable plastic surfaces. Of course these methods were unsuccessful since the acoustical attenuation features of the tile were seriously degraded by the coating process.
Therefore, there is a need for an inexpensive acoustical absorption panel suitable for clean-room environment in that it be washable and preferably hermetically sealed against the environment while still retaining full acoustical absorption characteristics within the specific acoustical frequency range to be absorbed.